• Title/Summary/Keyword: Mechanical interaction

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Numerical Study on the Pulsatile Blood Flow through a Bileaflet Mechanical Heart Valve and Leaflet Behavior Using Fluid-Structure Interaction (FSI) Technique (유체-고체 상호작용 (FSI)기법을 이용한 이엽기계식 인공심장판막을 지나는 혈액유동과 판첨거동에 관한 수치해석적 연구)

  • Choi, Choeng-Ryul;Kim, Chang-Nyung
    • The KSFM Journal of Fluid Machinery
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    • v.7 no.3 s.24
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    • pp.14-22
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    • 2004
  • Bileaflet mechanical valves have the complications such as hemolysis and thromboembolism, leaflet damage, and leaflet break. These complications are related with the fluid velocity and shear stress characteristics of mechanical heart valves. The first aim of the current study is to introduce fluid-structure interaction method for calculation of unsteady and three-dimensional blood flow through bileaflet valve and leaflet behavior interacted with its flow, and to overcome the shortness of the previous studies, where the leaflet motion has been ignored or simplified, by using FSI method. A finite volume computational fluid dynamics code and a finite element structure dynamics code have been used concurrently to solve the flow and structure equations, respectively, to investigate the interaction between the blood flow and leaflet. As a result, it is observed that the leaflet is closing very slowly at the first stage of processing but it goes too fast at the last stage. And the results noted that the low pressure is formed behind leaflet to make the cavitation because of closing velocity three times faster than opening velocity. Also it is observed some fluttering phenomenon when the leaflet is completely opened. And the rebounce phenomenon due to the sudden pressure change of before and after the leaflet just before closing completely. The some of time-delay is presented between the inversion point of ventricle and aorta pressure and closing point of leaflet. The shear stress is bigger and the time of exposure is longer when the flow rate is maximum. So it is concluded that the distribution of shear stress at complete opening stage has big effect on the blood damage, and that the low-pressure region appeared behind leaflet at complete closing stage has also effect on the blood damage.

Direct Simulation of the Magnetic Interaction of Elliptic Janus Particles Suspended in a Viscous Fluid (점성유체에 분산된 타원형 야누스 입자의 자성 상호작용에 관한 직접수치해석)

  • Kim, Hei Eun;Kang, Tae Gon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.7
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    • pp.455-462
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    • 2017
  • The magnetic interaction between elliptic Janus magnetic particles are investigated using a direct simulation method. Each particle is a one-to-one mixture of paramagnetic and nonmagnetic materials. The fluid is assumed to be incompressible Newtonian and nonmagnetic. A uniform magnetic field is applied externally in a horizontal direction. A finite-element-based fictitious domain method is employed to solve the magnetic particulate flow in the creeping flow regime. In the magnetic problem, the magnetic field in the entire domain, including the particles and the fluid, is obtained by solving the governing equation for the magnetic potential. Then, the magnetic forces acting on the particles are calculated via a Maxwell stress tensor formulation. In a single particle problem, it is found that the orientation angle at equilibrium is affected by the aspect ratio of the particle. As for the two-particle interaction, the dynamics and the final conformation of the particles are significantly influenced by the aspect ratio, the orientation, and the spatial positions of the particles. For the given positions of the particles, the fluid flow is also influenced by the orientation of each particle. The self-assembly structure of the particles is not a fixed one, but it varies with the above-mentioned factors.

Performance Enhancement Study Using Passive Control of Shock-Boundary Layer Interaction in a Transonic/Supersonic Compressor Cascade (천음속/초음속 압축기 익렬에서 Shock-Boundary Layer 상호작용의 수동적 제어에 의한 성능 향상 연구)

  • Kim, Sang-Deok;Gwon, Chang-O;Sa, Jong-Yeop
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.9
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    • pp.2944-2952
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    • 1996
  • In this paper the CSCM type upwind flux difference splitting Navier-Stokes method has been applied to study the ARL-SL19 transoni $c^ersonic compressor cascade flow. First, the general characteristics of baseline cascade flow were analyzed. At freestream Mach n.1.612 and exit/inlet pressure ratio 2.15, the results from current laminar flow were compared well in suction surface with the experiment; however, not well in pressure surface. Second, numerical study of the transoni $c^ersonic compressor cascade flow demonstrated the effectiveness of a passive control by the various size cavities. A cavity under the shock foot point at the suction surface of the blades was used as a passive control. The passive control of shock-boundary layer interaction by a cavity reduced total pressure losses. The effect of cavity length and depth was studied. The total pressure loss was reduced by about 10% and the isentropic efficiency was improved slightly. The effect of cavity depth in current study(d/l = 0.05, 0.02) was not found strong. Further adequate turbulence modeling and TVD schemes would help to capture the shock more accurately and increase the effectiveness of the current shock-boundary layer interaction study using upwind flux difference splitting computational methods.thods.

Two-Way Coupled Fluid Structure Interaction Simulation of a Propeller Turbine

  • Schmucker, Hannes;Flemming, Felix;Coulson, Stuart
    • International Journal of Fluid Machinery and Systems
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    • v.3 no.4
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    • pp.342-351
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    • 2010
  • During the operation of a hydro turbine the fluid mechanical pressure loading on the turbine blades provides the driving torque on the turbine shaft. This fluid loading results in a structural load on the component which in turn causes the turbine blade to deflect. Classically, these mechanical stresses and deflections are calculated by means of finite element analysis (FEA) which applies the pressure distribution on the blade surface calculated by computational fluid dynamics (CFD) as a major boundary condition. Such an approach can be seen as a one-way coupled simulation of the fluid structure interaction (FSI) problem. In this analysis the reverse influence of the deformation on the fluid is generally neglected. Especially in axial machines the blade deformation can result in a significant impact on the turbine performance. The present paper analyzes this influence by means of fully two-way coupled FSI simulations of a propeller turbine utilizing two different approaches. The configuration has been simulated by coupling the two commercial solvers ANSYS CFX for the fluid mechanical simulation with ANSYS Classic for the structure mechanical simulation. A detailed comparison of the results for various blade stiffness by means of changing Young's Modulus are presented. The influence of the blade deformation on the runner discharge and performance will be discussed and shows for the configuration investigated no significant influence under normal structural conditions. This study also highlights that a two-way coupled fluid structure interaction simulation of a real engineering configuration is still a challenging task for today's commercially available simulation tools.

Investigation of a fiber reinforced polymer composite tube by two way coupling fluid-structure interaction

  • Daricik, Fatih;Canbolat, Gokhan;Koru, Murat
    • Coupled systems mechanics
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    • v.11 no.4
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    • pp.315-333
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    • 2022
  • Fluid-Structure Interaction (FSI) modeling is highly effective to reveal deformations, fatigue failures, and stresses on a solid domain caused by the fluid flow. Mechanical properties of the solid structures and the thermophysical properties of fluids can change under different operating conditions. In this study, we investigated the interaction of [45/-45]2 wounded composite tubes with the fluid flows suddenly pressurized to 5 Bar, 10 Bar, and 15 Bar at the ambient temperatures of 24℃, 66℃, and 82℃, respectively. Numerical analyzes were performed under each temperature and pressure condition and the results were compared depending on the time in a period and along the length of the tube. The main purpose of this study is to present the effects of the variations in fluid characteristics by temperature and pressure on the structural response. The variation of the thermophysical properties of the fluid directly affects the deformation and stress in the material due to the Wall Shear Stress (WSS) generated by the fluid flow. The increase or decrease in WSS directly affected the deformations. Results show that the increase in deformation is more than 50% between 5 Bar and 10 Bar for the same operating condition and it is more than 100% between 5 Bar and 15 Bar by the increase in pressure, as expected in terms of the solid mechanics. In the case of the increase in the temperature of fluid and ambient, the WSS and Von Mises stress decrease while the slight increases of deformations take place on the tube. On the other hand, two-way FSI modeling is needed to observe the effects of hydraulic shock and developing flow on the structural response of composite tubes.

A Passive Control of Interaction of Condensation Shock Wave anc Boundary Layer(I) (응축충격파와 경계층 간섭의 피동제어(I))

  • Choe, Yeong-Sang;Jeong, Yeong-Jun;Gwon, Sun-Beom
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.2
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    • pp.316-328
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    • 1997
  • There were appreciable progresses on the study of shock wave / boundary layer interaction control in the transonic flow without nonequilibrium condensation. But in general, the actual flows associated with those of the airfoil of high speed flight body, the cascade of steam turbine and so on accompany the nonequilibrium condensation, and under a certain circumstance condensation shock wave occurs. Condensation shock wave / boundary layer interaction control is quite different from that of case without condensation, because the droplets generated by the result of nonequilibrium condensation may clog the holes of the porous wall for passive control and the flow interaction mechanism between the droplets and the porous system is concerned in the flow with nonequilibrium condensation. In these connections, it is necessary to study the condensation shock wave / boundary layer interaction control by passive cavity in the flow accompanying nonequilibrium condensation with condensation shock wave. In the present study, experiments were made on a roof mounted half circular arc in an indraft type supersonic wind tunnel to evaluate the effects of the porosity, the porous wall area and the depth of cavity on the pressure distribution around condensation shock wave. It was found that the porosity of 12% which was larger than the case of without nonequilibrium condensation produced the largest reduction of pressure fluctuations in the vicinity of condensation shock wave. The results also showed that wider porous area, deeper cavity for the same porosity of 12% are more favourable "passive" effect than the cases of its opposite. opposite.

A Study of Interaction Effect from Spray Fan Formed by Impinging Jets (충돌분류에 의해 형성된 Spray fan의 간섭효과에 관한 연구)

  • Han, J.S.;Kim, S.J.;Moon, D.Y.;Kim, Y.
    • Journal of the Korean Society of Propulsion Engineers
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    • v.3 no.3
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    • pp.9-15
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    • 1999
  • The Analysis of spray characteristics for combined spray group are necessary to develop large rocket engine. In this study, basic effects of interaction from spray fan formed by impinging jets were investigated with respect to mass distribution, droplet velocities and diameter. Patternater and PDPA are used for experimental apparatus. Water was used as a test fluid When momentum ratio is 1, effect of interaction from collision of spray fan on mass distribution are small. Also, effect of interaction from collision of spray fan on droplet velocities and diameter are small. But, droplet diameter is smaller near collision point due to second collision. Therefor, for the same momentum ratio from spray fan formed by impinging jets, we may neglect effect of interaction on mass distribution, droplet velocities and diameter.

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Harmonized Non-linear Interaction Between Different Two Vortex Shedding Frequencies (서로 다른 두 개의 와류방출 주파수간의 비선형간섭)

  • Kim, Sang Il;Seung, Sam Sun;Lee, Seung-Chul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.3
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    • pp.211-217
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    • 2014
  • This study analyzes the nonlinear interaction between two different vortex shedding frequencies from a cylinder with two diameters. In particular, two different vortex shedding frequencies are generated by preparing a cylinder having two diameters artificially. Flow velocity fluctuations behind the cylinder are measured three-dimensionally. Additionally, we fabricated a hole and placed a pressure transducer for measuring the pressure on the cylinder surface. The pressure signal from the pressure transducer is used as basic signal. A TSC(Trans Spectrum Coherence) is used for checking the strength of the nonlinear interaction between two different vortex shedding frequencies. As a result, the following are clarified: i) frequency distribution behind the cylinder, ii) three-dimensional flow state behind the cylinder through calculation of ensemble average, and iii) close relationship between the vertical vortex and change of low frequency by nonlinear interaction between two different vortex shedding frequencies from the cylinder with two diameters.

Study on the Performance of a Centrifugal Compressor Using Fluid-Structure Interaction Method (유체-구조 연성해석을 이용한 원심압축기 운전익단간극과 성능 예측)

  • Lee, Horim;Kim, Changhee;Yang, Jangsik;Son, Changmin;Hwang, Yoonjei;Jeong, Jinhee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.6
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    • pp.357-363
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    • 2016
  • In this study, we perform a series of aero-thermo-mechanical analyses to predict the running-tip clearance and the effects of impeller deformation on the performance using a centrifugal compressor. During operation, the impeller deformation due to a combination of the centrifugal force, aerodynamic pressure and the thermal load results in a non-uniform tip clearance profile. For the prediction, we employ the one-way fluid-structure interaction (FSI) method using CFX 14.5 and ANSYS. The predicted running tip clearance shows a non-uniform profile over the entire flow passage. In particular, a significant reduction of the tip clearance height occurred at the leading and trailing edges of the impeller. Because of the reduction of the tip clearance, the tip leakage flow decreased by 19.4%. In addition, the polytrophic efficiency under operating conditions increased by 0.72%. These findings confirm that the prediction of the running tip clearance and its impact on compressor performance is an important area that requires further investigation.